This invention relates to a thermoelectric power generating device and more particularly to a direct current power supply for a temperature controlled thermoelectric cooling or heating device.
Numerous electrical systems such as, for example, intrusion detectors include an infrared (IR) energy detector. Some IR detectors must be cooled for proper operation; while, others must be heated to preselected temperatures and maintained at these temperatures for the detectors to detect, for example, body heat radiating from an intruder. Thermoelectric coolers for these detectors require a direct current power source. To make these thermoelectric coolers economically available to the public, batteries have been used to power the coolers thereby eliminating the requirement for relatively expensive ac to dc convertors.
The present invention includes a transducer for converting thermal energy into electrical energy, such as, for example, a thermoelectric power generator. The thermoelectric generator generates a direct current (dc) for a thermoelectric heat pump. The thermoelectric heat pump is selectively connected to the thermoelectric power generator to provide the desired polarity for selectively cooling and heating, for example, an IR detector.
Another feature of the invention is to provide thermal energy for the thermoelectric power generator by means of an ac power supply. The ac power supply circuit includes a control circuit and a heater element for selectively supplying thermal energy to the thermoelectric heat pump.
Still another feature of the invention is to provide a temperature sensing network for sensing the temperature of a thermoelectric heat pump. The temperature sensing network includes a thermally sensitive resistor (thermistor) operable with a resistor of a temperature setting potentiomenter to control the operation of a zero voltage control switch. Thus when the resistance of the thermistor substantially equals that of the temperature set point resistor the zero voltage control switch inhibits the trigger pulses to a triac to cut off ac power to a heater element.
Other features and advantages of the present invention will be apparent to persons skilled in the art of the following detailed description of a preferred embodiment when read in conjunction with the attached drawings.